Find right sibling of a binary tree with parent pointers | C # program to print right sibling of a node ; A Binary Tree Node ; Constructor ; Method to find right sibling ; GET Parent pointer whose right child is not a parent or itself of this node . There might be case when parent has no right child , but , current node is left child of the parent ( second condition is for that ) . ; Move to the required child , where right sibling can be present ; find right sibling in the given subtree ( from current node ) , when level will be 0 ; Iterate through subtree ; if no child are there , we cannot have right sibling in this path ; This is the case when we reach 9 node in the tree , where we need to again recursively find the right sibling ; Driver Program to test above functions ; passing 10
using System ; public class Right_Sibling { public class Node { public int data ; public Node left , right , parent ; public Node ( int data , Node parent ) { this . data = data ; left = null ; right = null ; this . parent = parent ; } } public static Node findRightSibling ( Node node , int level ) { if ( node == null node . parent == null ) { return null ; } while ( node . parent . right == node || ( node . parent . right == null && node . parent . left == node ) ) { if ( node . parent == null node . parent . parent == null ) { return null ; } node = node . parent ; level -- ; } node = node . parent . right ; while ( level < 0 ) { if ( node . left != null ) { node = node . left ; } else if ( node . right != null ) { node = node . right ; } else { break ; } level ++ ; } if ( level == 0 ) { return node ; } return findRightSibling ( node , level ) ; } public static void Main ( string [ ] args ) { Node root = new Node ( 1 , null ) ; root . left = new Node ( 2 , root ) ; root . right = new Node ( 3 , root ) ; root . left . left = new Node ( 4 , root . left ) ; root . left . right = new Node ( 6 , root . left ) ; root . left . left . left = new Node ( 7 , root . left . left ) ; root . left . left . left . left = new Node ( 10 , root . left . left . left ) ; root . left . right . right = new Node ( 9 , root . left . right ) ; root . right . right = new Node ( 5 , root . right ) ; root . right . right . right = new Node ( 8 , root . right . right ) ; root . right . right . right . right = new Node ( 12 , root . right . right . right ) ; Console . WriteLine ( findRightSibling ( root . left . left . left . left , 0 ) . data ) ; } }